Influence of polarization and a source model for dose calculation in MRT
Stefan Bartzsch1, Michael Lerch2, Marco Petasecca2
1The Institute of Cancer Research, 15 Cotswold Road, Belmont, Sutton, Surrey SM2 5NG, United Kingdom and Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
Medical Physics
|April 4, 2014
Summary
Photon polarization has minimal impact on Microbeam Radiation Therapy (MRT) dose and peak to valley dose ratios within the target field. Simplified phase space models can improve dose calculations for MRT, aiding faster algorithms.
Area of Science:
- Medical Physics
- Radiation Oncology
- Biophysics
Background:
- Microbeam Radiation Therapy (MRT) offers a promising preclinical strategy for treating malignant tumors, including brain tumors, with potentially reduced side effects on healthy tissues.
- Accurate dose measurement and calculation in MRT are complex due to stringent spatial accuracy requirements and significant dose gradients.
- Monte Carlo simulations are used for dose calculations but are computationally intensive, and their accuracy, particularly concerning photon polarization, remains under investigation.
Purpose of the Study:
- To investigate the influence of photon polarization on dose distribution and peak to valley dose ratios (PVDRs) in Microbeam Radiation Therapy (MRT).
- To analyze the impact of detailed phase space information on MRT dose calculations.
- To evaluate a simplified source model for dose calculations in MRT.
Main Methods:
- Monte Carlo simulations using the Geant4 toolkit were employed to assess polarization effects on dose and PVDRs.
- Phase space information from prior research was analyzed for its influence on peak and valley doses.
- A simplified parallel beam source model was developed and validated through semi-adjoint Monte Carlo simulations, with results compared to experimental data.
Main Results:
- Photon polarization significantly affects scattered dose outside the primary microbeam field.
- Within the radiation field, dose and PVDRs calculated with and without polarization showed less than a 3% difference.
- Phase space details, including inhomogeneous flux and beam geometry, influenced valley doses by approximately 10%, aligning with measurement uncertainties.
Conclusions:
- Photon polarization has a minor impact on clinically relevant peak and valley doses within the MRT field.
- A simplified phase space model is suitable for MRT dose calculations, facilitating the development of faster dose calculation algorithms.
- The characterization of the MRT source for clinical trials supports the use of these simplified models.
More Related Videos
Related Concept Videos
02:59Biological Effects of Radiation
15.4K
All radioactive nuclides emit high-energy particles or electromagnetic waves. When this radiation encounters living cells, it can cause heating, break chemical bonds, or ionize molecules. The most serious biological damage results when these radioactive emissions fragment or ionize molecules. For example, α and β particles emitted from nuclear decay reactions possess much higher energies than ordinary chemical bond energies. When these particles strike and penetrate matter, they...
15.4K
01:15Pharmacodynamic Models: Linear Concentration–Effect Model
91
The linear concentration–effect model, underpinned by the principle that pharmacological effect (E) is directly proportional to plasma drug concentration (C), emerges as a pivotal simplification of the Emax model for conditions where C is significantly less than EC50. This model portrays a linear trajectory of the concentration–effect relationship when drug levels are markedly below the EC50 threshold.Despite its inherent assumption of continuous effect augmentation with increasing...
91